1. Field of the Invention
The present invention relates generally to seed depositing implements, and more particularly to a seed metering drive mechanism having improved ground-driven gauge wheel and overriding clutch constructions.
2. Discussion of the Prior Art
In the use of conventional planters, it is known to provide a seed metering drive mechanism for measuring the speed of the implement, and controlling the rate at which seeds are deposited. A conventional construction includes a pair of laterally spaced gauge wheels adapted to roll across the ground, and a drive means for transmitting the rotational drive of the gauge wheels through a counter shaft and transmission to a metering drive shaft connected to each of the planter units on the implement. Thus, metering of the seeds is controlled by the drive mechanism.
The gauge wheels in a conventional construction support the implement above the ground, and may include structure for adjusting the height of the implement. In addition, a compression spring is provided in association with each gauge wheel for biasing the wheel toward the ground so that the wheels remain in contact with the ground as the planter travels over uneven ground. When the height of the implement is adjusted, the displacement of the spring is altered such that the biasing force exerted on the gauge wheel differs for differing implement heights. In order to remedy this shortcoming, conventional constructions provide structure for readjusting the spring displacement each time the height is changed.
There is a need with conventional metering drive mechanisms to permit the gauge wheels to be mounted either forward of or to the rear of the tool bar of the implement. By providing this adaptability, it is possible to accommodate different types of hitch and towing implements. In conventional constructions, it is sometimes possible to remove the gauge wheels completely from the tool bar, reverse their orientation, and reassemble them on the implement. However, this is difficult to carry out, and involves disassembly and reassembly of both wheel mounts.
During operation of a conventional planter, drive from both gauge wheels is transmitted to a single counter shaft, and it is necessary to employ an overriding clutch between the counter shaft and each gauge wheel so that the wheels are free to rotate relative to one another. By providing this construction, the implement is free to turn or to plant on a radius without creating torque problems in the counter shaft or slippage of the wheels.
On a conventional planter, the distance between the gauge wheels may range from 15-60 feet such that the difference in speed between the two wheels differs substantially as the planter travels along a radiused path. The provision of an overriding clutch between the counter shaft and each gauge wheel permits the counter shaft to be driven by the faster gauge wheel, while disengaging the shaft from the slower wheel.
A problem encountered with conventional drive mechanisms arises because of the size of available overriding clutches. For example, conventional clutches have a thickness greater than the thickness of other sprockets that are to be used in the transmission, and sometimes occupy 2.5 inches or more of space on the counter shaft. As a result, guarding shields designed to cover the overriding clutch and other transmission elements must be large enough to accommodate the clutch, and therefore use more material and space than is desirable.